Polythiophenes have been studied extensively due to their interesting electrical and/or optical properties. Polythiophenes become electrically conducting upon chemical or electrochemical oxidation or reduction. Their ultimately achievable electrical conductivity is determined by their chemical composition, the stereoregularity of the polymerization of the thiophene monomers in the polythiophene chain and by their π-conjugation lengths. Such stereoregularity problems do not arise when unsubstituted thiophenes or thiophenes substituted in the 3- and 4-positions with identical groups are polymerized.
WO 00/65653 discloses a method in the fabrication of an organic thin-film semiconducting device, wherein the semiconducting device comprises an electrode arrangement with electrodes contacting a semiconducting organic material, and wherein the method is characterized by depositing a first layer of a conducting or semiconducting material in the form of a combination of a conducting and a semiconducting material in the form of a patterned or non-patterned layer on an insulating substrate, such that at least a portion of the substrate is covered by the first layer; modifying the work function of the conducting layer and/or semiconducting material of the first layer by depositing a second layer of a conducting polymer with a work function higher than that of the material in the first layer such that the layer of the conducting polymer mainly covers the first layer or is conformal with the latter, whereby the combination of the first layer and the second layer constitutes the anode of the electrode arrangement and the work function of the anode becomes substantially equal to that of the conducting polymer, depositing a third layer of a semiconducting organic material on the top of the anode, and optionally and in casse only a portion of the substrate is covered by the anode, also above at least some of the portion of the substrate not covered by the anode; and depositing a paterned or non-patterned fourth layer of a meatl on the top of the third layer, whereby the fourth layer constitutes the cathode of the electrode arrangement. WO 00/65653 discloses that the conducting polymer in the second layer is a doped conjugated polymer e.g. poly(3,4-ethylenedioxythiophene) (PEDOT), a copolymer which includes the monomer 3,4-ethylenedioxythiophene, substituted poly(thiophenes), substituted poly(thiophenes), substituted poly(pyrroles), substituted poly(anilines) or copolymers thereof, with the dopant being preferably poly(4-styrene sulphonate) (PSS).
WO 00/06665 discloses an electroluminescent device comprising a light-emitting organic film, arranged between an anode material and a cathide material such that under an applied voltage, the device is forward biased and holes are injected from the anode material into the organic film adjacent to the anode material and electrons are injected from the cathode material into the organic film adjacent to the cathode material, resulting in light emission from the light-emitting organic film; wherein the device additionally comprises a solution-processed film of a blend of an acid-functional non-conductive polymer e.g. polymers having pendant groups selected from sulfonic acid, sulfinic acid, carboxylic acid, phosphoric acid, phosphonic acid, phosphinic acid, and —N+(R)2H where R is selected from hydrogen, C1–C20 hydrocarbyl, hydroxy, alkoxy, and aryloxy, and a conductive polymer positioned between the anode material and the light-emitting organic film, wherein the weight ratio of non-conducting to conducting polymer is at least 0.75:1. WO 00/0665 specifically discloses the following non-conductive polymers: sulfonated polyphenylenes, polyphenylenes bearing carboxylic acid functional groups, poly(styrene sulfonic acid), poly(2-acrylamido-2-methyl-1-propanesulfonic acid), polyacrylic acid, polymethacrylic acid or a mixture thereof.
U.S. Pat. No. 5,111,327 discloses an electro-responsive polymer comprising chemically combined repeat units selected from the class consisting of,
and a mixture thereof where R is a member selected from hydrogen or a C(1-18)organic radical.
EP-A 1 122 274 discloses a process for preparing water-soluble π-conjugated polymers, characterized in that the monomer thiophene derivative according to formula (I)
in which X and Y are independently O, S, N—R1, Z is —(CH2)m—CR2R3—(CH2)n—; R1 is aryl, C1-18-alkyl or hydrogen; R2 is hydrogen or —(CH2)s—O—(CH2)p—SO3−M+; R3 is —(CH2)s—O—(CH2)p—SO3−M+; M+ is a cation; m and n are independently a whole number from 0 to 3; s is a whole number from 0 to 10; and p is a whole number from 1 to 18; is polymerized by an oxidation agent in aqueous solution.
WO 01/78464 discloses in an organic/polymer electroluminescent(EL) device which comprises: a transparent substrate; a semitransparent electrode deposited on the transparent substrate; a hole-injecting layer positioned on the semitransparent electrode; an emissive layer made of an organic EL-material, positioned on the hole-injecting layer; and electron-injecting layer positioned on the electron-injecting layer, the improvement comprising that single-ion conductors are employed for the hole-injecting layer and the electron-injecting layer. The specification does not define the meaning of the term “single-ion conductor”, which in plain language means a conductor of a single ion, although claim 9 teaches that the single ion conductor can be a single-cation conductor or a single anion conductor and claim 10 teaches that such single ion conductors can be represented as a general formula (I) or (II), comprising ether chain [(—CH2)nO—] such as polyethylene oxide or polypropylene oxide in the main chain, and contains anions such as SO3−, COO− or I− in the main side chains that form ionic bonds with counter ions such as Na+, Li+, Zn2+, Mg2+, Eu3+, or (NH3)4+:
wherein, EO represents ethylene oxide; Non-EO represents non-ethylene oxide; PO represents propylene oxide; Non-PO represents non-propylene oxide; A− represents anion; C+ represents cation; m+n=11 and n represents a real number more than 0 and less than 1.
T.-W. Lee and O. O. Park disclosed in 2001 in Advanced Materials, volume 13, pages 1274–1278, polymer light-emitting energy-well devices using single-ion conductors (SIC's) in which charge injection and its confinement simultaneously in EL devices is striven for by using both a single-cationic conductor (SCC) and a single-anionic conductor (SAC), which “greatly improve the charge injection due to accumulation of the mobile ions near the electrodes” with the aim of “confining well-electrons and holes leading to enhanced recombination rate of the pairs” in devices in which “the mobile ions to play a key role in improvement of charge injection are separately located near both electrodes in the structure of a sandwiched multi-layer device instead of blending with the emitting material so that the problem of phase separation of the emitting materials can be avoided”. They further disclose that ionic polyurethane possesses good mechanical properties and high ionic conductivity with a single-ion transport character and that SIC's are generally of two different types: one is a polymer blend of an ionomer and polyether which usually possesses poor mechanical properties and the other is the copolymer of an oligomeric ionomer with polyether. They also disclosed that incorporation of the SIC's with soft and hard blocks into the EL devices dramatically improves not only luminance but also the efficiency and that SCC's possess electron-injecting and hole-blocking properties and SAC's possess hole-injecting and electron-blocking properties.
T.-W. Lee et al. disclosed in 2001 in Journal of Applied Physics, volume 90, pages 2128–2134, a study of the effect of ion concentration, neutralization level and counterions in ionomers to obtain the optimal electroluminescent (EL) characteristics in polymer light-emitting diodes using poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) for the emissive layer and sulphonated polystyrene (SPS) ionomers for the electron-injecting layer.
A general problem in electronic devices, particularly in light emitting diodes, is undesirable hole-electron recombination at the positive electrode thereby reducing the efficiency and lifetime of the device.